Close the socket gracefully on Windows

[BewareMyPower]

Fixes #261

Motivation

When closing the socket on Windows, the ERROR_CONNECTION_ABORTED error might be returned in the callback of async_receive. It's caused by the socket::close method is not portable enough, see https://www.boost.org/doc/libs/1_81_0/doc/html/boost_asio/reference/basic_stream_socket/close/overload2.html

For portable behaviour with respect to graceful closure of a connected socket, call shutdown() before closing the socket.

Modifications

Call shutdown in ClientConnection::closeSocket before calling close. In addition, when no bytes are returned or the eof error happened, print the logs with debug level whatever the error code is in the read callback.

Documentation

• doc-required
  (Your PR needs to update docs and you will update later)

• doc-not-needed
  (Please explain why)

• doc
  (Your PR contains doc changes)

• doc-complete
  (Docs have been already added)

[BewareMyPower]

Here are some tests results with debug logs based on this patch.

Without calling shutdown, the error log is always:

# error code: connection_aborted ("The network connection was aborted by the local system")
2023-06-14 13:14:15.190 DEBUG [11468] ..\..\..\lib\ClientConnection:615 | [[::1]:10740 -> [::1]:6650] Server closed the connection:  由本地系统中止网络连接。

With calling shutdown, the error log will be:

# error code: operation_aborted ("Operation cancelled")
2023-06-14 13:15:08.607 DEBUG [21080] ..\..\..\lib\ClientConnection:613 | [[::1]:10745 -> [::1]:6650] Read operation was canceled: 由于线程退出或应用程序请求，已中止 I/O 操作。

There is a little chance that the error code could be eof (value() is 2 on Windows) when I debugged it in my IDE so I handled the EOF error the same way with bytesTransferred == 0 because they both mean the socket client calls recv while the socket server has already closed.